In the past, various different types of timer devices, such as defrost timers or the like for instance, have been utilized in various different apparatus or domestic appliances, such as refrigerators, freezers, heat pumps and air conditioners or the like, to controllably cycle a defrost heater thereof. The defrost heater is, of course, energized on a timed or periodic basis for automatically removing or melting frost or ice which may form on evaporators or other heat absorbing elements of the above discussed apparatus or domestic appliances and which may impair the operating efficiency thereof. In many of these past timer devices, a timer or synchronous motor was utilized to rotatably drive a cam which actuated a switch on a timed basis to controllably energize and deenergize the defrost heater, such as a heating coil or the like, connected in circuit relation with such switch.
Due to changing weather, atmospheric or climate conditions, the formation of frost on the evaporators of the aforementioned apparatus is, of course, at different rates, and it may not be necessary to defrost such apparatus, i.e., energize the heating coil thereof, as often when the frost is formed at a slower rate. Thus, it may be advantageous to delay or extend the defrost time interval or time period between successive energizations of the defrost heating coil by the defrost timer operably associated therewith, and such extension of the defrost time interval also serves to conserve energy which is advantageous in the light of the recent energy crisis.
One of the past defrost timers included a pair of alternate cams for actuating a switch thereof to controllably energize an associated defrost heating coil. However, in order to increase the periods between the energization of the defrost heating coil, it was necessary to physically reassemble one of the alternate cams in the switch operating place of the other alternate cam. Thus, at least one disadvantageous or undesirable feature of the aforementioned one past defrost timer is believed to be the necessity to interchange the alternate cams in order to increase the defrost time interval between defrost cycles. Of course, in order to effect the interchange of the alternate cams, as discussed above, it may have also been necessary to deenergize the apparatus and/or at least partially dismantle the defrost timer thereof which are also believed to be ancilliary disadvantageous features.
In another of the past defrost timers, a pair of cams were arranged generally in side-by-side relation, and the cam pair each had different peripheral configurations, i.e. rises and falls, arranged at least in part in overlaying relation to effect the actuation of a following switch which, in turn, controllably energized and deenergized an associated defrost heating coil. At least one of the disadvantageous or undesirable features of the aforementioned another past defrost timer is believed to be that it was necessary to operate or rotatably drive the cam pair conjointly at the same speed due to the overlaying relation of the cam pair. Another disadvantageous feature of the another past defrost timer is believed to be that the speed thereof was dictated by the cam cycles and necessarily was operated at the slowest speed, i.e. of the two cam cycles. Furthermore, since the operation of the another past defrost timer is believed to be at a relatively slow speed, a snap-acting switch was utilized in following relation with the cam pair which may have effected critical switch adjustments.